GRANTS PASS, Ore. — What is the potential impact of a major offshore earthquake on dams in Oregon and southern Washington?

That is the question the U.S. Army Corps of Engineers is trying to answer through a study which is about halfway completed.

Dam safety program manager Matt Craig said Monday the agency doesn’t expect any of the dams to fail to the point of losing their reservoirs, but there could be some damage.

The Cascadia Subduction Zone last let go more than 300 years ago, but scientists say it could go again at any time. If it does, it is expected to produce an earthquake and tsunami similar to what hit Japan two years ago.

Since starting the studies 15 years ago, the corps has studied earthquake dangers at 10 dams.